1. Field of the Invention
The present invention relates LCD devices and more particularly to a lamp-connection socket, and a backlight unit and LCD device using the same.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) device displays desired images by controlling the transmittance of light emitted from a backlight unit.
Backlight units are generally classified as either edge-type backlight units or direct-type backlight units depending on the position of fluorescent lamp.
The edge-type backlight unit is generally used for small-sized LCD devices such as notebook computers, while the direct-type backlight unit is more commonly used for large-sized LCD devices such as televisions.
The related art direct-type backlight unit includes a plurality of fluorescent lamps where high voltage electrical power is provided from an inverter through a wire to each of the fluorescent lamps. The related art direct-type backlight unit uses a plurality of transformers to drive the fluorescent lamps, resulting in complicated structures and high fabrication cost.
To simplify the structure and decrease the fabrication cost in the related art direct-type backlight unit, the direct-type backlight units have been developed that use a parallel driving method in which the plurality of fluorescent lamps are driven in parallel.
The direct-type backlight unit using the parallel driving method is provided with an inverter that includes a common electrode and a transformer. The common electrode is connected to each of the respective fluorescent lamps, and the transformer applies a high voltage to the common electrode. However, the direct-type backlight unit of the parallel driving method has the disadvantage that some of the fluorescent lamps may not turn on upon application of power to the common electrode, because the current applied through the common electrode will flow largely to those fluorescent lamps having a low resistance value after being initially turned on.
In the case of the direct-type backlight unit employing the parallel driving method, a ballast capacitor is connected to an electrode included in each of the fluorescent lamps. Thus, a balanced current may be maintained within the respective fluorescent lamps, even when the plurality of fluorescent lamps is driven in parallel. The ballast capacitor may be included in the inverter connected to the transformer supplying the voltage to the electrode of each fluorescent lamp, or may be formed in a PCB substrate holding the common electrode.
Accordingly, the related art direct-type backlight unit using the parallel driving method has the following disadvantages.
In the related art direct-type backlight unit using the parallel driving method, the inverter or the PCB having the common electrode is increased in size due to the area occupied by the ballast capacitor and the connection structure of lamp is complicated.